}

        return asStream(form.docId).contentType(getImageMimeType(thumbnailFile)).stream(out -> {
            try (BufferedInputStream in = new BufferedInputStream(new FileInputStream(thumbnailFile))) {
                out.write(in);
            }
        });
    }

    protected String getImageMimeType(final File imageFile) {
        final String path = imageFile.getAbsolutePath();